I do a combination of things.
First, I sweep all the existing brass as far forward of the line as possible before I start shooting.
Second, I stand one to two steps back from the line. As others have mentioned, this keeps most of the brass from bouncing forward.
Third, I color the extractor groove in my brass with a red Sharpie and tell the guys on either side that if they see brass with a red ring, it's mine - people are pretty good about giving me my brass back if I ask.
Fourth, once I'm done, I sweep anything with a red ring that has fallen forward of the line back toward me if I can reach it with the broom.
I average 95% recovery with 9 mm & .45 ACP and about 90% with .40 S&W. I'm not the only person at my indoor range who reloads so only 3/4 of the people look at me funny. Actually, when I mention the red ring to people, they usually start asking questions about reloading.